Dr. Salih Kocak

This paper investigated the use of high percentage recycled asphalt pavement (RAP) in combination with crumb rubber (CR) and ethylene-glycidyl-acrylate terpolymer for asphalt pavement maintenance applications. Hot asphalt mixtures were prepared according to the Superpave hot mix asphalt protocol. Combined mixtures were prepared with 40% RAP and single mesh size #20 CR modifier using a wet process (hereinafter CRW) and 40% RAP and ethylene-glycidyl-acrylate terpolymer (hereinafter EGA). Additionally, full RAP (100% RAP) mixtures prepared by petroleum-based rejuvenator and a conventional cold patching mixture (CPM) were studied to compare the relative mixture performances since pavement maintenance activities like pothole patching have historically been carried out with CPMs. All binders were modified using the same PG58-28 base binder. Dynamic modulus testing for linear viscoelastic characterization, flow number (FN) testing for rutting potential, and indirect tensile strength testing (ITS) for thermal cracking were conducted to assess the relative performance of the mixtures. The results revealed that the environmentally friendly and sustainable 100% hot RAP mixture and CRW and EGA combination mixtures outperformed the typical CPM in laboratory performance tests.

The use of recycled/reclaimed asphalt pavement (RAP) provides not only economic but also environmental benefits. However, increasing the percentage of RAP in a new asphalt pavement may hinder the economic benefits due to the necessity of expensive softer binders used to compensate for RAP stiffening effect. Alternatively, this problem may potentially be overcame by use of another recycled material; crumb rubber (CR). In this study, the thermal and fatigue cracking performances of the mixtures prepared with rubberized, soft and base binders were compared. The crumb rubber modification methods and binders included in this study were (i) devulcanized rubber, (ii) crumb rubber terminally blend, (iii) crumb rubber wet process, (iv) soft binder (PG 58-34) and (v) base binder (PG 58-28). The results of the fatigue tests indicated that all crumb rubber modified asphalt mixtures made with the base binder (PG58-28) outperformed the mixture made with grade bumped (PG58-34) binder. Similar results were observed in low temperature cracking tests. These results indicated that the crumb rubber modified binders can be used in lieu of grade bumping in high RAP mixtures. In fatigue cracking tests, among the three crumb rubber technologies, wet process outperformed terminally blend and devulcanized rubber at high temperatures and high strain levels at low temperatures. At relatively low strain levels, terminally blend was the best performer in low temperature. In low temperature cracking tests, devulcanized rubber exhibited highest tensile strength, but lowest fracture energy. Wet process exhibited highest fracture energy and lowest strength.

Noise pollution is a growing concern in the United States and other countries. While there are many sources of noise, traffic noise is a major portion of total noise in the environment. A major component of traffic noise is the sound generated by the interaction of tires with the roadway. At high speeds, (>30 miles/hr) tire/pavement noise overshadows the noise from other sources in the vehicle. This paper presents a novel sound propagation and generation modeling technique that can be used in roadway applications including environmental impact studies of roadways and other noise sources, development of noise maps, and barrier design …etc. The model also has capability of simulating generation of sound. The model is based on one of the most efficient computational fluid dynamic techniques, the Lattice Boltzmann (LB) method. Unlike existing wave propagation models, this model simulates air pressure fluctuations (i.e., sound waves) at the tire/pavement interface by solving the Navier-Stokes equations for air. The details of the LB method and its validation using analytical solutions and laboratory measurements have been given. Furthermore, several example applications of LB method for sound propagation as well as sound generation problems have been presented.